Conventionally, refrigerating apparatuses performing a refrigeration cycle by circulating refrigerant in a refrigerant circuit have been known and are widely used in air conditioners and the like. For example, Patent Document 1 discloses a refrigerating apparatus including a compressor for compressing refrigerant and an expander for expanding the refrigerant to recover motive power. Specifically, in a refrigerating apparatus shown in FIG. 1 in Patent Document 1, the expander is connected to the compressor through a single shaft so that the motive power obtained in the expander is utilized for driving the compressor. In another refrigerating apparatus shown in FIG. 6 in Patent Document 1, a motor and a generator are connected to the compressor and the expander, respectively, so that the compressor is driven by the motor to compress the refrigerant while the generator is driven by the expander to generate motive power.
A fluid machinery in which an expander and a compressor are connected to each other through a single shaft is disclosed in Patent Document 2, for example. In the fluid machinery disclosed in this patent document, a compression mechanism as a compressor, an expansion mechanism as an expander, and a shaft connecting them are housed in a single casing. Further, in this fluid machinery, an oil supply path is formed inside the shaft to supply lubricant oil reserved in the bottom of the casing to the compression mechanism and the expansion mechanism through the oil supply path.
Patent Document 3 discloses a generally-called hermetic compressor in which a compression mechanism and a motor are housed in a single casing. In the hermetic compressor, an oil supply path is formed in a drive shaft of a compression mechanism so that lubricant oil reserved in the bottom of the casing is supplied to the compression mechanism through the oil supply path. The refrigerating apparatus shown in FIG. 6 in Patent Document 1 may use a hermetic compressor of this kind.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2000-241033    Patent Document 2: Japanese Unexamined Patent Application Publication No. 2005-299632    Patent Document 3: Japanese Unexamined Patent Application Publication No. 2005-002832